Dear Liz: I am confused about “safe withdrawal rates” from retirement accounts. I’ve read that withdrawing 4% of savings each year is the gold standard that financial planners utilize to ensure that life savings are preserved in retirement.

However, if the Standard & Poor’s 500 index returns on average 8% a year, and if the life savings are locked down in a mutual fund that is indexed to the S&P 500, then shouldn’t the annual withdrawal amount, to preserve those savings, be 8%? Limiting my withdrawals to 4% means my retirement would be pushed several years down the road. Can you clarify?

Answer: It’s good you asked this question before you retired, rather than afterward when it might have been too late.

You’re right that on average, the S&P 500 has returned at least 8% annualized returns in every rolling 30-year period since 1926. (“Rolling” means each 30-year period starting in 1926, then 1927, then 1928, and so on.)

But the market doesn’t return 8% each and every year. Some years are up a lot more. And some are down — way down. In 2008, for example, the S&P 500 lost about 37% of its value in a single year.

Such big downturns are especially risky for retirees, because retirees are drawing money from a shrinking pool of assets. The money they withdraw doesn’t have the chance to benefit from the inevitable rebound when stock prices recover. Bad markets, particularly at the beginning of someone’s retirement, can dramatically increase the odds of running out of money.

Inflation also can vary, as can returns on cash and bonds. All these factors play a role in how long a pot of money can be expected to last. The “4% rule” resulted from research by financial planner William Bengen, who in the 1990s examined historical returns from 1926 to 1976. Bengen found there was no period when an initial 4% withdrawal, adjusted each year afterward for inflation, would have exhausted a diversified investment portfolio of stocks and bonds in less than 33 years.

Some subsequent research has suggested a 3% initial withdrawal rate might be better, especially for early retirees or those with more conservative, bond-heavy portfolios.

Free online calculators can give you some idea of whether you’re on track to retire. A good one to check out is T. Rowe Price’s retirement income calculator. But you’d be smart to run your findings past a fee-only financial planner as well. The decisions you make in the years around retirement are often irreversible, and what you don’t know can hurt you.

One of the “givens” I often see in discussions about retirement is the idea that previous generations didn’t have much of one. Great-grandpa got to the end of his working life, got his gold watch and keeled over.

Short or non-existent retirements certainly were the rule before the 20th century. People usually worked until they died or until they were physically unable to continue. There were some exceptions; Civil War pensions allowed older veterans to leave the workforce earlier and some companies launched mandatory retirement policies in the late 1800s. The fact remains, though, that many people ended their lives in abject poverty because they could no longer work. That was what prompted the creation of Social Security in the 1930s.

It’s not true, though, that people in the 20th century died shortly after turning 65. That’s obvious from this table of historical life expectancies compiled by the Social Security Administration.

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Check out the last two columns. Even in 1940, men could expect to nearly 13 more years and women nearly 15. Life expectancies at age 65 have certainly gotten longer (20% longer for men, 33% for women) since 1940. The bigger change has been in the percentage of people making it to 65. Improving safety standards and better health care meant a whole lot more people got a shot at having a retirement.

(And these figures don’t account for reductions in infant and childhood mortality, since the numbers in the second two columns reflect adult survival rates from age 21 to 65.)

Another big change came in 1961, when the earliest age for collecting Social Security benefits dropped to age 62. That plus longer life expectancies contributed to lengthier retirements.

The trend seems to be reversing. The average retirement age for men has risen in the past 20 years from 62 to 64. The average retirement age for women also increased from 59 to 62.

That still leaves a lot of years to support yourself, which is why delaying retirement and working part-time in retirement are often good strategies for making your savings last.

Dear Liz: I’m 64 and lost my last full-time job a year ago. I have since exhausted my unemployment benefits and been on and off food stamps. (I’m waiting to get back on them right now because my temporary-to-permanent job didn’t become permanent after all.) Fortunately I almost never need to go to a doctor, or if I do, I don’t know that I do and can’t afford to find out. I have about $3,000 in emergency savings, and my IRA is about $15,000. I was fortunate enough to sell a home in Hawaii 20 years ago, but I managed to run through all the money. My income when I was working full time was only $26,000 a year. I don’t know what to do, and I don’t know why I listen to all these financial programs that seem to target twentysomethings or people with retirement savings and comfortable incomes. They do not speak to my situation. My priority isn’t saving for retirement. It’s paying the bills.

Answer: Financial programs are, at least to some extent, concerned about the entertainment value of their programming. They often focus on people who fit their audience demographics and whose problems have satisfying solutions. That’s why the people featured tend to be younger or to have resources, because those are the ones who typically can recover from past mistakes and get their finances on track.

When people have no income, there’s not much financial advice to give. And when they’re in their 60s and have virtually no retirement savings, there’s no way to “catch up.”

That doesn’t mean your situation is hopeless, but it does mean you’ll have to hustle to stay afloat.

Finding a full-time job at this point is a long shot, so part-time work and Social Security probably will provide your income in the coming years. Social Security might replace as much as 40% of your previous low income (the replacement rate is lower for higher earners), but that still leaves you with a substantial gap to fill.

Ideally, you would hold out until age 66 before applying so you can get your full Social Security benefit. You’re eligible for benefits now, but your checks will be permanently reduced if you start early and your earnings could potentially reduce your check further under the earnings test (which you can learn more about at http://www.ssa.gov/oact/cola/rtea.html). The benefits that are withheld aren’t lost, because at full retirement age your monthly check would be increased to account for the withholdings. You’ll have to balance whether those disadvantages outweigh the upside of starting a guaranteed income now.

By the way, if you’ve ever been married and the marriage lasted at least 10 years, you may qualify for spousal or survivor benefits (even if the marriage ended in divorce) that could exceed the benefit you’ve earned on your own record. You can discuss your options by calling the Social Security Administration at (800) 772-1213.

You’ll need to look for ways to reduce your expenses so that you can get by on whatever income you receive. If you qualify, the federal Section 8 program could help pay for housing (start at Benefits.gov to see what programs are available). Some of the other ways to reduce housing costs — the biggest expense for most people — include getting a roommate, becoming a live-in caregiver for an older person or a family with kids, or becoming an apartment manager or the caretaker of a property.

At 65, you’ll qualify for Medicare. Although this government health insurance program for older Americans doesn’t cover everything, you will have access to healthcare again.

Dear Liz: None of the Web-based tools I’ve seen really get at the heart of the problem of how much I really need in retirement. For example, if I am diligent and save 20% of my income (I earn over $150,000), why would I need to replace 95% or even 80% of my income to maintain my standard of living in retirement? If I subtract the 20% going to savings, another 10% for the costs of working (clothes, lunches, gas) and reduce my income tax 5%, shouldn’t I be living the same lifestyle at 65% of my current income? Now, if I have a pension that will replace 10% of my pay, and if Social Security benefits for my spouse and me replace 30%, don’t my investments have to produce only the remaining 25%? Or am I missing something?

Answer: The further you are from retirement, the harder it can be to predict how much you’ll need when you get there.

Financial planners often use an income replacement rate of 70% to 80% as a starting point. It’s just that, though. Planners will tell you some of their clients’ spending actually increases in the early years of retirement as they travel and indulge in other expensive hobbies. Those who are frugal or used to living well below their means are often able to retire comfortably with a much lower income replacement rate.

A big wild card is the cost of medical and nursing care in your later years. The U.S. Bureau of Labor Statistics’ Consumer Expenditure Survey shows average overall spending tends to drop after retirement and continues to decline as people age. Serious illness or a nursing home bill can cause spending to surge late in life, however, leading to a U-shaped spending pattern for many.

Taxes also are hard to predict. While most people drop into a lower tax bracket once they stop working, those with substantial retirement incomes and investments may not. Tax rates themselves could rise in the future, even if your income doesn’t.

Social Security benefits may change, as well. Although it’s highly unlikely the program will disappear, some proposals for changing Social Security reduce checks for higher earners.

Once you’re within a decade or so of retirement, you should have a better handle on what you’ll spend once you quit work. Before that point, err on the side of caution. Assuming a higher income replacement rate gives you wiggle room once you’ve retired — or the option to retire earlier if it turns out you need less.